Cochliomyia hominivorax

 	
  Chrysomya bezziana


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Reported

Cochliomyia hominivorax (Coquerel)

Eradicated

Chrysomya bezziana (Villeneuve)

Reported

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FURTHER INFORMATION

“A Manual for the Diagnosis of Screw-Worm Fly” J.P. Spradbery, AFFA, 2002

“Manual for the Control of the Screwworm Fly Cochliomyia hominivorax, Coquerel”, FAO, 1989

FAO website - http://www.fao.org Search for ‘screwworm’ and / or ‘myiasis’

Maps show the approximate distribution of screwworm flies at the time of

printing. For current and more detailed information on the distribution of

screwworm fly in a particular country, the government veterinary agencies

of that country should be contacted.

	

	
			
		




	
	
 
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SCREWWORM 1. BIOLOGY, DISTRIBUTION AND SCREWWORM IDENTIFICATION

1. BIOLOGY, DISTRIBUTION AND

IDENTIFICATION

Copyright 2008 - IAEA

The following people and organisations kindly provided photos and drawings:

Australian Government Department of Agriculture, Fisheries and Forestry (DAFF); Mexican-American

Commission for the Eradication of Screwworm - Mexico; CSIRO Entomology - Australia; U. Feldmann

& M. Vreysen, Joint FAO/IAEA Division - Austria; J.P. Spradbery, XCS Consulting - Australia; Natural

History Museum courtesy of M. J. R. Hall - United Kingdom; FAO courtesy of J. Slingenbergh - Italy; J.

Kucharski, USDA/ARS - USA; W. Snow, formally National Screwworm Eradication Programme - Jamaica.

Review of the poster content was kindly provided by Dr Martin Hall (Natural History Museum, United Kingdom),

Dr Rod Mahon (CSIRO Entomology, Australia), Dr Philip Spradbery (XCS Consulting, Australia) and Dr Rudolf

Urech (Queensland Department of Primary Industries and Fisheries, Australia).

Adult screwworm flies and larvae at a wound.

















First instar

Second instar

Third instar

• Adults mate within a couple of days after emerging from

the soil.

• Males: • sexually mature within 24 hours.

• may mate five to six times.

• Females: • sexually mature within 2 or 3 days.

• generally mate only once.

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Anterior spiracle

6 to 12 lobes

(usually 7 to 9)

3 to 7 lobes

(usually 4 to 6)

Darkly pigmented to segment

9 or 10

Not darkly pigmented

except in the posterior half

of segment 12

12 11 10 9

Tracheal

trunks






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• Each female capable of laying several egg masses

during her lifetime.

• Egg masses laid on or near an open wound of a

living animal.

• 100 to 300 eggs per egg mass.

• Laid in a pattern like roof-tiles.

• White, cigar-shaped, approximately 1 mm long.

• Hatch 10 - 12 hours later.

After hatching from the egg, three stages or instars of

larvae (also known as maggots).

• First instar larvae are white, small (up to 3 mm

long); crawl into the wound and start feeding on

living tissues; duration: 1 day.

• Second instar larvae are white to cream in colour,

(up to 7 mm long); continue eating on living flesh;

duration: 1 day.

• Third instar larvae are white to cream in colour,

when mature change to pinkish colouration, (up to

17 mm long); further enlarge the wound; duration:

3 - 5 days.

• Head of mature third instar larva with dark mouth

hooks.

• Mouth hooks used to tear at the host tissues

during feeding.

• Larvae form dense aggregations.

• Larvae feed with their heads buried downwards

in the wound.

• Only posterior larval ends exposed to the surface.

• Spiracles on the posterior end used to obtain

oxygen from the air.

• ‘Myiasis’ is a term used to refer to the presence

of fly larvae in a wound.

• Mature third instar larvae exit wound and drop to

ground, usually at shaded places, where animals

rest during the day.

• Larvae burrow 2 - 3 cm below soil surface.

• Larva develops into a pupa inside the darkening

larval skin (’puparium’).

• Puparia are brownish in colour approximately 10 mm

long.

• Pupal period depends on temperature, from 7 days

in warm conditions to 65 days in winter.

• After emerging from puparium, adult burrows

to soil surface, where wings extend fully. Adult

then flies away.

• Up to 10 mm long.

• Variously coloured from metallic blue to bluish

purple or blue-green.

• Eyes reddish in colour.

• Live for about 2 weeks.

• Harmless apart from their ability to lay eggs

on the wounds of animals.

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